In addition to their art and cultural heritages, Jogja and surrounding areas have also an importa... more In addition to their art and cultural heritages, Jogja and surrounding areas have also an important and interesting geoheritage. In areas not far from Jogja, within radius around 40 km and only one day visiting, there are characteristic and important rock exposures that can be reached easily because their locations are nearby the asphalted roads. These exposures are very special due to geological informations they contain. The informations include a whole story of the lifetime of an ancient volcanic arc of Java known as the Oligo-Miocene Arc or called the Old Andesite Formation (AOF), “the backbone of Java Island”, which forms the southern part of Java Island. The story is a polyhistory consisting of periods with different geological events. These events consist of pre-OAF, syn-OAF and post-OAF. The pre-OAF period is a non-volcanic period as shown by the outcrops of Pre-Tertiary basement and Paleogene carbonate and silisiclastic rocks in Bayat areas. The syn-OAF period comprises thr...
2ND INTERNATIONAL CONFERENCE ON EARTH SCIENCE, MINERAL, AND ENERGY
Java is an island which is considered to be quite disaster-prone. This terminology comes from the... more Java is an island which is considered to be quite disaster-prone. This terminology comes from the fact that along the island, we can find subduction tectonic activities which is also an epicenter. Some earthquake phenomena can be extremely destructive because of the existence of active fault as the vibration medium. Therefore, it is very important to do active fault mapping in Java island. In East Java province, there is an active fault which has been researched many times called Grindulu Fault. It is an active fault located in Pacitan Regency, East Java Province. It is a left-lateral fault. It is well exposed 500m alongside Grindulu river. However, the continuity of Grindulu northward is not well identified due to limitation of outcrop. This research was conducted to see how far the continuity of Grindulu northward. This research was started by satellite imagery survey to view areas where the existence of Grindulu fault may be found. Furthermore, field data acquisition was done on the marked areas. Field data obtained were in the form of fault slip data which were then analyzed using Wintensor software to see their kinematics. Based on the field data, the continuity of Grindulu fault can be found in three other areas which are Bakalan village, Wonogiri village; Pohijo village, Ponorogo regency; and Kruwe village, Megetan regency. Those exposed faults are strike-slip faults which are segments of massive NE-SW fault. This major fault is proposed with the name of Magetan-Pacitan active fault. The understanding of this active fault is expected to be reference for disaster mitigation in those areas.
The hydrogeological condition of a region is determined by the type of lithology, morphology, and... more The hydrogeological condition of a region is determined by the type of lithology, morphology, and subsurface conditions where the condition is very helpful in the study of groundwater exploration. Especially when we encounter interesting geological conditions when the groundwater exploration in the karst area in which volcanic rocks are resulting from the activities of the active volcano in the past. Groundwater exploration at Ponjong area and surrounding does have its special characteristics, because it has 2 different rock characteristics where the northern part of the research area in the form of a karst area (limestone of Wonosari Formation) while the southern part is an area of ancient volcanoes with dominant volcanic rocks from Wuni Formation, As for the research on the above and subsurface research area where the research is conducted based on surface geology mapping, geoelectric data collection, and groundwater sampling. Geological mapping includes geomorphological data, str...
Jiwo Hills is an isolated hill with approximately occupied 30 km2 in Bayat area of Central Java. ... more Jiwo Hills is an isolated hill with approximately occupied 30 km2 in Bayat area of Central Java. The Jiwo Hills has been considered to be composed of very low-grade metamorphic rocks. This contribution explains a preliminary view of the metamorphic rocks from collected rocks sample in the Jiwo Hills. Common metamorphic rocks found in this area are phyllite, mica schist, calc-silicate schist, and marble with the foliation trend of NE-SW. Most of the metamorphic rock exposures are strongly weathered. Rarely epidote-glaucophane schist crop out near the exposure of serpentinite in western part of this complex. Several carbonate sedimentary rocks are converted to garnet-wollastonite skarn under the contact metamorphism probably caused by diabase intrusion. Garnet-wollastonite skarn mainly consists of garnet and wollastonite embed in the quartz matrix. The garnets are rich of grossular composition, range from Adr13–19Grs81–85Sps0–2. Those show anisotropic, with sectorial twinning zonings. The skarn deposits might give important information for economic resources in this area. Epidote-glaucophane schist mainly consists of glaucophane, epidote, quartz, phengite, titanite, and hematite. By the present of this blueschist facies of high-pressure metamorphic rock in this area, it confirms that Jiwo Hills is one of the high-pressure metamorphic terranes together with Luk Ulo Complex of Central Java, Meratus Complex of South Kalimantan, and Bantimala Complex of South Sulawesi. The serpentinites might facilitate exhumation of the blueschist in the Jiwo Hills. Detailed study of the distribution of metamorphic rocks in this area is needed in order to understanding tectonic evolution as well as economic geology.
Kisar island is an enigmatic feature which reveals anomalous mountain building processes in the f... more Kisar island is an enigmatic feature which reveals anomalous mountain building processes in the forearc basin of the Banda arc-continent collision. The roughly circular uplift rises 3 km from the basin floor to the surface and is surrounded by uplifted coral terraces. The island is near a retrowedge thrust imaged by seismic reflection. Yet, the location, shape, and structures of
Field analyses of stratigraphy, structure, and tectonic geomorphology of Savu Island define the a... more Field analyses of stratigraphy, structure, and tectonic geomorphology of Savu Island define the age and provenance of accreted Australian continental margin sequences and overlying synorogenic cover, and the structure, kinematics, and uplift history of the transition from subduction to ...
ABSTRACT Coral terrace surveys and U-series ages of coral yield a surface uplift rate of ∼0.5 m/k... more ABSTRACT Coral terrace surveys and U-series ages of coral yield a surface uplift rate of ∼0.5 m/ka for Kisar Island, which is an emergent island in the hinterland of the active Banda arc–continent collision. Based on this rate, Kisar first emerged from the ocean as recently as ∼450 ka. These uplifted terraces are gently warped in a pattern of east–west striking folds. These folds are strike parallel to more developed thrust-related folds of similar wavelength imaged by a seismic reflection profile just offshore. This deformation shows that the emergence of Kisar is influenced by forearc closure along the south-dipping Kisar Thrust. However, the pinnacle shape of Kisar and the protrusion of its metamorphic rocks through the forearc basin sediments also suggest a component of extrusion along shear zones or active doming.Coral encrusts the island coast in many locations over 100 m above sea level. Terrace morphology and coral ages are best explained by recognizing major surfaces as mostly growth terraces and minor terraces as mostly erosional into older terraces. All reliable and referable coral U-series ages determined by MC-ICP-MS correlate with marine isotope stage (MIS) 5e (118–128 ka). The only unaltered coral samples are found below 6 m elevation; however an unaltered Tridacna (giant clam) shell in growth position at 95 m elevation yields a U-series age of 195 ± 31 ka, which corresponds to MIS 7. This age agrees with the best-fit uplift model for the island. Loose deposits of unaltered coral fragments found at elevations between 8 and 20 m yield U-series ages of <100 years and may represent paleotsunami deposits from previously undocumented tectonic activity in the region.
A major wrench zone, left-lateral slip in nature, strongly deformed a series of Late Oligocene to... more A major wrench zone, left-lateral slip in nature, strongly deformed a series of Late Oligocene to Pleistocene rocks in the northern coastal line of East Java and its eastern islands and offshore areas. The fault zone trends west – east forming a deformed zone of 15 to 40 km wide and 675 km long from Rembang area in the west through Madura Island and Kangean Islands to Sakala offshore area in the east. The deformed zone is called the Rembang- Madura-Kangean-Sakala (RMKS) Fault Zone. Based on the regional setting of East- and Southeast Sundaland, it is known that the RMKS Fault Zone occurred at the hinge belt or shelf edge to slope area of a geologic transition from the stable Eastern Sunda Shelf to the north (the Northern Platform) to the deep-water area to the south. There is a contrast of sedimentary facies to the north and south of the RMKS Fault Zone. Tectonically, the stable Eastern Sunda Shelf is considered to overlie the expected micro-continent called the Paternoster-Kangean. Therefore, the RMKS Fault Zone is located at the southern margin of the micro-continent. Basement lithology and configuration to the north and south of the RMKS Fault Zone are different. A number of mechanisms are considered to origin the RMKS Fault Zone. These include : the westward stress driven by the collision of the Buton-Tukang Besi and Banggai-Sula to the east of Sulawesi, westward stress due to the collision of Australia with Timor and anticlockwise bending of the Banda Arc, and northward stress due to the subduction of the Indian oceanic crust beneath Java. The initiation of the RMKS Fault Zone was in the upper Early Miocene in Sakala area and younger westward until the Middle Miocene in Rembang area. Along the RMKS Fault Zone, flower structures are definitely identified on seismic sections, showing basement-involved, deeply-rooted vertical master faults with upward diverging splays/strands that have mostly reverse separations. In map view, these splays are mapped as fold and fault belts trending west-east and west northwest-east southeast. Extensional component of the wrench zone subsided the Paleogene rifted blocks such as the Central Deep and formed a number of normal faults. Tectonic inversion related with both pure and simple shear deformations is observed along the fault zone. Shale diapirism commonly occurs to the south of the fault zone and its occurrence is related to wrench tectonism in thick shale sequences deposited rapidly to the south of the RMKS Fault Zone.
In addition to their art and cultural heritages, Jogja and surrounding areas have also an importa... more In addition to their art and cultural heritages, Jogja and surrounding areas have also an important and interesting geoheritage. In areas not far from Jogja, within radius around 40 km and only one day visiting, there are characteristic and important rock exposures that can be reached easily because their locations are nearby the asphalted roads. These exposures are very special due to geological informations they contain. The informations include a whole story of the lifetime of an ancient volcanic arc of Java known as the Oligo-Miocene Arc or called the Old Andesite Formation (AOF), “the backbone of Java Island”, which forms the southern part of Java Island. The story is a polyhistory consisting of periods with different geological events. These events consist of pre-OAF, syn-OAF and post-OAF. The pre-OAF period is a non-volcanic period as shown by the outcrops of Pre-Tertiary basement and Paleogene carbonate and silisiclastic rocks in Bayat areas. The syn-OAF period comprises thr...
2ND INTERNATIONAL CONFERENCE ON EARTH SCIENCE, MINERAL, AND ENERGY
Java is an island which is considered to be quite disaster-prone. This terminology comes from the... more Java is an island which is considered to be quite disaster-prone. This terminology comes from the fact that along the island, we can find subduction tectonic activities which is also an epicenter. Some earthquake phenomena can be extremely destructive because of the existence of active fault as the vibration medium. Therefore, it is very important to do active fault mapping in Java island. In East Java province, there is an active fault which has been researched many times called Grindulu Fault. It is an active fault located in Pacitan Regency, East Java Province. It is a left-lateral fault. It is well exposed 500m alongside Grindulu river. However, the continuity of Grindulu northward is not well identified due to limitation of outcrop. This research was conducted to see how far the continuity of Grindulu northward. This research was started by satellite imagery survey to view areas where the existence of Grindulu fault may be found. Furthermore, field data acquisition was done on the marked areas. Field data obtained were in the form of fault slip data which were then analyzed using Wintensor software to see their kinematics. Based on the field data, the continuity of Grindulu fault can be found in three other areas which are Bakalan village, Wonogiri village; Pohijo village, Ponorogo regency; and Kruwe village, Megetan regency. Those exposed faults are strike-slip faults which are segments of massive NE-SW fault. This major fault is proposed with the name of Magetan-Pacitan active fault. The understanding of this active fault is expected to be reference for disaster mitigation in those areas.
The hydrogeological condition of a region is determined by the type of lithology, morphology, and... more The hydrogeological condition of a region is determined by the type of lithology, morphology, and subsurface conditions where the condition is very helpful in the study of groundwater exploration. Especially when we encounter interesting geological conditions when the groundwater exploration in the karst area in which volcanic rocks are resulting from the activities of the active volcano in the past. Groundwater exploration at Ponjong area and surrounding does have its special characteristics, because it has 2 different rock characteristics where the northern part of the research area in the form of a karst area (limestone of Wonosari Formation) while the southern part is an area of ancient volcanoes with dominant volcanic rocks from Wuni Formation, As for the research on the above and subsurface research area where the research is conducted based on surface geology mapping, geoelectric data collection, and groundwater sampling. Geological mapping includes geomorphological data, str...
Jiwo Hills is an isolated hill with approximately occupied 30 km2 in Bayat area of Central Java. ... more Jiwo Hills is an isolated hill with approximately occupied 30 km2 in Bayat area of Central Java. The Jiwo Hills has been considered to be composed of very low-grade metamorphic rocks. This contribution explains a preliminary view of the metamorphic rocks from collected rocks sample in the Jiwo Hills. Common metamorphic rocks found in this area are phyllite, mica schist, calc-silicate schist, and marble with the foliation trend of NE-SW. Most of the metamorphic rock exposures are strongly weathered. Rarely epidote-glaucophane schist crop out near the exposure of serpentinite in western part of this complex. Several carbonate sedimentary rocks are converted to garnet-wollastonite skarn under the contact metamorphism probably caused by diabase intrusion. Garnet-wollastonite skarn mainly consists of garnet and wollastonite embed in the quartz matrix. The garnets are rich of grossular composition, range from Adr13–19Grs81–85Sps0–2. Those show anisotropic, with sectorial twinning zonings. The skarn deposits might give important information for economic resources in this area. Epidote-glaucophane schist mainly consists of glaucophane, epidote, quartz, phengite, titanite, and hematite. By the present of this blueschist facies of high-pressure metamorphic rock in this area, it confirms that Jiwo Hills is one of the high-pressure metamorphic terranes together with Luk Ulo Complex of Central Java, Meratus Complex of South Kalimantan, and Bantimala Complex of South Sulawesi. The serpentinites might facilitate exhumation of the blueschist in the Jiwo Hills. Detailed study of the distribution of metamorphic rocks in this area is needed in order to understanding tectonic evolution as well as economic geology.
Kisar island is an enigmatic feature which reveals anomalous mountain building processes in the f... more Kisar island is an enigmatic feature which reveals anomalous mountain building processes in the forearc basin of the Banda arc-continent collision. The roughly circular uplift rises 3 km from the basin floor to the surface and is surrounded by uplifted coral terraces. The island is near a retrowedge thrust imaged by seismic reflection. Yet, the location, shape, and structures of
Field analyses of stratigraphy, structure, and tectonic geomorphology of Savu Island define the a... more Field analyses of stratigraphy, structure, and tectonic geomorphology of Savu Island define the age and provenance of accreted Australian continental margin sequences and overlying synorogenic cover, and the structure, kinematics, and uplift history of the transition from subduction to ...
ABSTRACT Coral terrace surveys and U-series ages of coral yield a surface uplift rate of ∼0.5 m/k... more ABSTRACT Coral terrace surveys and U-series ages of coral yield a surface uplift rate of ∼0.5 m/ka for Kisar Island, which is an emergent island in the hinterland of the active Banda arc–continent collision. Based on this rate, Kisar first emerged from the ocean as recently as ∼450 ka. These uplifted terraces are gently warped in a pattern of east–west striking folds. These folds are strike parallel to more developed thrust-related folds of similar wavelength imaged by a seismic reflection profile just offshore. This deformation shows that the emergence of Kisar is influenced by forearc closure along the south-dipping Kisar Thrust. However, the pinnacle shape of Kisar and the protrusion of its metamorphic rocks through the forearc basin sediments also suggest a component of extrusion along shear zones or active doming.Coral encrusts the island coast in many locations over 100 m above sea level. Terrace morphology and coral ages are best explained by recognizing major surfaces as mostly growth terraces and minor terraces as mostly erosional into older terraces. All reliable and referable coral U-series ages determined by MC-ICP-MS correlate with marine isotope stage (MIS) 5e (118–128 ka). The only unaltered coral samples are found below 6 m elevation; however an unaltered Tridacna (giant clam) shell in growth position at 95 m elevation yields a U-series age of 195 ± 31 ka, which corresponds to MIS 7. This age agrees with the best-fit uplift model for the island. Loose deposits of unaltered coral fragments found at elevations between 8 and 20 m yield U-series ages of <100 years and may represent paleotsunami deposits from previously undocumented tectonic activity in the region.
A major wrench zone, left-lateral slip in nature, strongly deformed a series of Late Oligocene to... more A major wrench zone, left-lateral slip in nature, strongly deformed a series of Late Oligocene to Pleistocene rocks in the northern coastal line of East Java and its eastern islands and offshore areas. The fault zone trends west – east forming a deformed zone of 15 to 40 km wide and 675 km long from Rembang area in the west through Madura Island and Kangean Islands to Sakala offshore area in the east. The deformed zone is called the Rembang- Madura-Kangean-Sakala (RMKS) Fault Zone. Based on the regional setting of East- and Southeast Sundaland, it is known that the RMKS Fault Zone occurred at the hinge belt or shelf edge to slope area of a geologic transition from the stable Eastern Sunda Shelf to the north (the Northern Platform) to the deep-water area to the south. There is a contrast of sedimentary facies to the north and south of the RMKS Fault Zone. Tectonically, the stable Eastern Sunda Shelf is considered to overlie the expected micro-continent called the Paternoster-Kangean. Therefore, the RMKS Fault Zone is located at the southern margin of the micro-continent. Basement lithology and configuration to the north and south of the RMKS Fault Zone are different. A number of mechanisms are considered to origin the RMKS Fault Zone. These include : the westward stress driven by the collision of the Buton-Tukang Besi and Banggai-Sula to the east of Sulawesi, westward stress due to the collision of Australia with Timor and anticlockwise bending of the Banda Arc, and northward stress due to the subduction of the Indian oceanic crust beneath Java. The initiation of the RMKS Fault Zone was in the upper Early Miocene in Sakala area and younger westward until the Middle Miocene in Rembang area. Along the RMKS Fault Zone, flower structures are definitely identified on seismic sections, showing basement-involved, deeply-rooted vertical master faults with upward diverging splays/strands that have mostly reverse separations. In map view, these splays are mapped as fold and fault belts trending west-east and west northwest-east southeast. Extensional component of the wrench zone subsided the Paleogene rifted blocks such as the Central Deep and formed a number of normal faults. Tectonic inversion related with both pure and simple shear deformations is observed along the fault zone. Shale diapirism commonly occurs to the south of the fault zone and its occurrence is related to wrench tectonism in thick shale sequences deposited rapidly to the south of the RMKS Fault Zone.
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Common metamorphic rocks found in this area are phyllite, mica schist, calc-silicate schist, and marble with the foliation trend of NE-SW. Most of the metamorphic rock exposures are strongly weathered. Rarely epidote-glaucophane schist crop out near the exposure of serpentinite in western part of this complex. Several carbonate sedimentary rocks are converted to garnet-wollastonite skarn under the contact metamorphism probably caused by diabase intrusion.
Garnet-wollastonite skarn mainly consists of garnet and wollastonite embed in the quartz matrix. The garnets are rich of grossular composition, range from Adr13–19Grs81–85Sps0–2. Those show anisotropic, with sectorial twinning zonings. The skarn deposits might give important information for economic resources in this area.
Epidote-glaucophane schist mainly consists of glaucophane, epidote, quartz, phengite, titanite, and hematite. By the present of this blueschist facies of high-pressure metamorphic rock in this area, it confirms that Jiwo Hills is one of the high-pressure metamorphic terranes together with Luk Ulo Complex of Central Java, Meratus Complex of South Kalimantan, and Bantimala Complex of South Sulawesi. The serpentinites might facilitate exhumation of the blueschist in the Jiwo Hills. Detailed study of the distribution of metamorphic rocks in this area is needed in order to understanding tectonic evolution as well as economic geology.
offshore areas. The fault zone trends west – east forming a deformed zone of 15 to 40 km wide and 675 km long from Rembang area in the west through Madura Island and Kangean
Islands to Sakala offshore area in the east. The deformed zone is called the Rembang- Madura-Kangean-Sakala (RMKS) Fault Zone.
Based on the regional setting of East- and Southeast Sundaland, it is known that the RMKS Fault Zone occurred at the hinge belt or shelf edge to slope area of a geologic transition from the stable Eastern Sunda Shelf to the north (the Northern Platform) to the deep-water area to the south. There is a contrast of sedimentary facies to the north and south of the RMKS Fault Zone. Tectonically, the stable Eastern Sunda Shelf is considered to overlie the expected micro-continent called the Paternoster-Kangean. Therefore, the RMKS Fault Zone is located at the southern margin of the micro-continent. Basement lithology and configuration to the north and south of the RMKS Fault Zone are different.
A number of mechanisms are considered to origin the RMKS Fault Zone. These include : the westward stress driven by the collision of the Buton-Tukang Besi and Banggai-Sula to the
east of Sulawesi, westward stress due to the collision of Australia with Timor and anticlockwise bending of the Banda Arc, and northward stress due to the subduction of the Indian
oceanic crust beneath Java. The initiation of the RMKS Fault Zone was in the upper Early Miocene in Sakala area and younger westward until the Middle Miocene in Rembang area.
Along the RMKS Fault Zone, flower structures are definitely identified on seismic sections, showing basement-involved, deeply-rooted vertical master faults with upward diverging
splays/strands that have mostly reverse separations. In map view, these splays are mapped as fold and fault belts trending west-east and west northwest-east southeast. Extensional
component of the wrench zone subsided the Paleogene rifted blocks such as the Central Deep and formed a number of normal faults. Tectonic inversion related with both pure and simple shear deformations is observed along the fault zone. Shale diapirism commonly occurs to the south of the fault zone and its occurrence is related to wrench tectonism in thick shale
sequences deposited rapidly to the south of the RMKS Fault Zone.
Common metamorphic rocks found in this area are phyllite, mica schist, calc-silicate schist, and marble with the foliation trend of NE-SW. Most of the metamorphic rock exposures are strongly weathered. Rarely epidote-glaucophane schist crop out near the exposure of serpentinite in western part of this complex. Several carbonate sedimentary rocks are converted to garnet-wollastonite skarn under the contact metamorphism probably caused by diabase intrusion.
Garnet-wollastonite skarn mainly consists of garnet and wollastonite embed in the quartz matrix. The garnets are rich of grossular composition, range from Adr13–19Grs81–85Sps0–2. Those show anisotropic, with sectorial twinning zonings. The skarn deposits might give important information for economic resources in this area.
Epidote-glaucophane schist mainly consists of glaucophane, epidote, quartz, phengite, titanite, and hematite. By the present of this blueschist facies of high-pressure metamorphic rock in this area, it confirms that Jiwo Hills is one of the high-pressure metamorphic terranes together with Luk Ulo Complex of Central Java, Meratus Complex of South Kalimantan, and Bantimala Complex of South Sulawesi. The serpentinites might facilitate exhumation of the blueschist in the Jiwo Hills. Detailed study of the distribution of metamorphic rocks in this area is needed in order to understanding tectonic evolution as well as economic geology.
offshore areas. The fault zone trends west – east forming a deformed zone of 15 to 40 km wide and 675 km long from Rembang area in the west through Madura Island and Kangean
Islands to Sakala offshore area in the east. The deformed zone is called the Rembang- Madura-Kangean-Sakala (RMKS) Fault Zone.
Based on the regional setting of East- and Southeast Sundaland, it is known that the RMKS Fault Zone occurred at the hinge belt or shelf edge to slope area of a geologic transition from the stable Eastern Sunda Shelf to the north (the Northern Platform) to the deep-water area to the south. There is a contrast of sedimentary facies to the north and south of the RMKS Fault Zone. Tectonically, the stable Eastern Sunda Shelf is considered to overlie the expected micro-continent called the Paternoster-Kangean. Therefore, the RMKS Fault Zone is located at the southern margin of the micro-continent. Basement lithology and configuration to the north and south of the RMKS Fault Zone are different.
A number of mechanisms are considered to origin the RMKS Fault Zone. These include : the westward stress driven by the collision of the Buton-Tukang Besi and Banggai-Sula to the
east of Sulawesi, westward stress due to the collision of Australia with Timor and anticlockwise bending of the Banda Arc, and northward stress due to the subduction of the Indian
oceanic crust beneath Java. The initiation of the RMKS Fault Zone was in the upper Early Miocene in Sakala area and younger westward until the Middle Miocene in Rembang area.
Along the RMKS Fault Zone, flower structures are definitely identified on seismic sections, showing basement-involved, deeply-rooted vertical master faults with upward diverging
splays/strands that have mostly reverse separations. In map view, these splays are mapped as fold and fault belts trending west-east and west northwest-east southeast. Extensional
component of the wrench zone subsided the Paleogene rifted blocks such as the Central Deep and formed a number of normal faults. Tectonic inversion related with both pure and simple shear deformations is observed along the fault zone. Shale diapirism commonly occurs to the south of the fault zone and its occurrence is related to wrench tectonism in thick shale
sequences deposited rapidly to the south of the RMKS Fault Zone.